This application incorporates by reference Taiwanese application Serial No. 89120708, filed Oct. 4, 2000.
1. Field of the Invention
The invention relates in general to an ink-jet output control method, and more particularly to a control method for an ink-jet output device using a step motor.
2. Description of the Related Art
The step motor and servo motor are the two most popular types of motor used in image positioning control for ink-jet output devices such as printers, facsimiles and multi-function machines. Since the servo motor is too expensive, most low-priced ink-jet output devices use the step motor as the source of power for the reciprocating movement of the printhead carriage. The step motor adopts an open loop control system whereby the printhead carriage""s velocity of movement during printing is controlled. The advantages of the step motor include low price, easy control and less time error during operation. As the ink-jet printhead is mounted on the print-head carriage, the printhead will proceed a reciprocating movement to facilitate printing when the carriage is driven by the step motor.
Step motors, whose driving method includes full-step, half-step and micro-step, are further categorized as two-phase, three-phase, four-phase and five-phase step motors. The micro-step driving method can provide a higher position resolution. However, the ordinary step motor installed in an ink-jet output device to drive the printhead carriage still fails to produce adequate mechanic resolution despite the application of the micro-step motor. In order to improve printing resolution, interpolation is implemented in every step to improve the distribution of ink dots.
Please refer to FIG. 1, which is a graph showing the relationship between the stepping motor velocity xcfx89 and the time T. As shown in FIG. 1, from a macro view, the motor proceeds with a constant angular acceleration 102 movement from a still state, carries out constant speed printing with a constant angular velocity 104 movement and returns to the still state after a constant angular deceleration 106. The time interval in each step is larger during low speed than in high speed. For example, the time interval in a second step 108, xcex94t2, is larger than the time interval in an nth step 110, xcex94tn.
From a micro view, the motor experiences a process of acceleration/deceleration during an actual magnetizing operating velocity 112 in each step. That is to say, the motor achieves a maximum angular acceleration 114 in the magnetizing transient and proceeds with the process of angular deceleration after a maximum angular velocity 116 has been reached, and achieves a minimum angular velocity 118 before the next magnetizing occurs. Since the speed of the printhead carriage cannot be controlled in a real constant speed movement, a real even interpolation and quality printing cannot be achieved if the motor adopts an equal time interval interpolation in each step.
It is therefore an object of the invention to provide an ink-jet output method, according to every velocity change of the motor, which proceeds with an ink-jet interpolation in unequal time intervals to achieve an even distribution of ink dots.
To achieve the above-mentioned object, an ink-jet output control method is provided to control the printing quality of ink-jet output devices, wherein the ink-jet output device includes a printhead, a printhead carriage and a step motor used to drive the printhead carriage under a variety of velocity models. The above-mentioned printhead can jet out a number of ink drops in each step of the step motor. The ink-jet output control method includes: firstly, to set a number of time pulse values of every two adjacent ink dots in each step of the step motor under different velocity models, and store these set values, which are non-identical in a memory unit. Next, the printhead determines the time interval of ink-jet signal sending according to these time pulse values, and ink dots are spread on a recording medium in unequal time intervals as the printhead receives ink-jet control signals.
The foregoing time pulse setting method that controls ink-jet outputting includes the experimental revision method, theoretical deduction method and so on. The experimental revision method is as follows: firstly, proceed with equal time interval interpolation in each step of the step motor""s rotation to produce several ink dots with unequal distance intervals. Next, having observed the distances between ink dots, adjust the time pulse values of every two adjacent ink dots to obtain several non-identical time pulse values so that every two adjacent ink dots are approximately of the same distance. Lastly, record and store the time pulse values of the ink dots as pre-stored data in a memory unit.
The foregoing time pulse setting method that controls ink-jet outputting further includes the theoretical deduction method, which is as follows: firstly, proceeding with equal time interval interpolation in each step of the step motor""s rotation produces several ink dots of unequal distances. Next, having observed the distances and calculated the time pulse values of every two adjacent ink dots, the distances between ink dots will be approximately equal. Lastly, several non-identical time pulse values will be obtained and used as pre-stored data in a memory unit.